Marine drilling structure with curved drill conductor

ABSTRACT

The invention relates to a marine structure of the type normally anchored into the substratum of an offshore body of water. The structure includes a work deck which is supported beyond the water&#39;&#39;s surface to position drilling, processing and other equipment ancillary to a subsea well producing operation. The supporting faction includes a plurality of downwardly reaching support legs that anchor into the substratum by means of piles or other fastening means. The platform is further provided with horizontal bracing, which positions a series of conductor guide units substantially one above the other, whereby a cylindrical drill conductor can be driven from the working deck, through the respective guide units, to be deflected into a predetermined curvature.

United States Patent Mott et al. [45] June 20, 1972 54' M 1 DRILLING STRUCTURE WITH 3,451,493 6/1969 S t grm.... .....17s/9 CURVED DRILL CONDUCTOR 3,474,630 10/1969 Pogonowski ..61/46.'s

[72] Inventors: George E. Mott, Metairie; Johnnie J.

mary Examiner-Jacob Shapiro zmber Morgan Clty both of Attorney-Thomas H. Whaley and Carl G. Reis [73] Assignee: Texaco Inc., New York, N.Y. 22 Filed: Sept. 17, 1970 [57] 21 Appl. No.2 72,911

The invention relates to a marine structure of the type normally anchored into the substratum of an offshore body of water. The structure includes a work deck which is supported [52] US. Cl. ..6l/46.5, 175/5, l75/7, beyond the water's surface to position drilling, processing and l75/61 other equipment ancillary to a subsea well producing opera- I z": li l'l- The supporting faction includes a plurality of [58] Field 0? Search ..6l/46.5, 72.3, 72.1, 69; downwardly reaching support legs that anchor i the b,

175/ 61; 66/5, stratum by means of piles or other fastening means. The platform is further provided with horizontal bracing, which posi- [56] References cited tions a series of conductor guide units substantially one above UNITED STATES PATENTS the other, whereby a cylindrical drill conductor can be driven from the working deck, through the respective guide units, to 3,3 l Hauber et ai. ...6l/46.5 be deflected into a predetermined cu vature 3,004,612 10/1961 Kofahl i 175/7 3,472,035 10/ 1969 Broussard et a]. ..61/72.3 10 Claims, 6 Drawing figures Z? 21 L1 I "I *F f Yd 7F PA'TE'N'TEDmzo 1972 SHEET 10F 2 MARINE DRRLING STRUCTURE WITH CURVED DRILL CONDUCTOR BACKGROUND OF THE INVENTION In the exploratory drilling of an offshore field for the purpose of determining the field's potential productivity, it is often expedient to provide as many exploratory and/or producing wells from each platform as possible. In the instance of a floating type drill ship, the ship is merely floated from one location to another, whereby a series of vertical wells can be drilled. In the instance of an anchored platform however the problem of obtaining maximum exploratory coverage from a single location embodies some difficulty.

To obtain the maximum exploratory or producing coverage of any oil rich reservoir, it has been found feasible to employ the technique of drilling a number of wells from a single, fixed base. The usual facility or base comprises an anchored platform which is fixedly positioned to the floor of the body of water. With the platform so anchored, presently known drilling techniques permit a plurality of wells to be directionally oriented whereby to in essence radiate away from the fixed drilling center.

Where the potentially productive area is relatively close to the ocean floor, it can be difficult to sufficiently deflect a drill string to have wells enter the desired substrate at a sufiicient distance from the platform to permit drilling numerous wells. This is true since, for directionally adjusting the drill in any operation, such adjustment must be made rather gradually thereby requiring a predetermined depth of solid substrate through which to drill.

One expedient for readily achieving a number of directionally drilled wells, is to provide a platform having fixed,'sloping drill conductors which commence at the platforms deck and direct the drill string at a predetermined angle to the ocean floor. This drilling technique however necessitates the use of deck mounted equipment capable of being adjusted to conform to the angle at which the drill conductor is aligned. Such equipment is considered a specialty item, and consequently relatively expensive in contrast to the normal uprightly disposed drilling rig.

Toward overcoming the herein stated problems, and toward achieving the desired drilling apparatus, for progressively deviating an offshore well, there is presently provided a unique structure. The latter is capable of being anchored to an offshore location whereby to drill one or more directional wells radiating away from the structure in the direction and number as required. The structure includes in essence, a work deck which is disposed above the waters surface. A plurality of support legs extend downwardly from the deck and are connected at the lower ends thereof to the ocean floor. Bracing members further embody conductor guide means and are so arranged on the platform to sequentially register and accommodate various conductor pipes lowered therethrough. The cylindrical conductor is thus deflected from an initial vertical stance, into a curved orientation.

DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates in side elevation, a structure of the type contemplated including one curved drill conductor fully set, as well as a second conductor in a partially set condition.

FIG. 2 is a top view of the platform shown in FIG. 1.

FIG. 3 is a cross-sectional view on an enlarged scale taken along line 3-3 in FIG. 1.

FIG. 4 is an alternate embodiment of the guide member shown in FIG. 3.

FIG. 5 is a cross-sectional view on an enlargedscale taken along line 55 in FIG. 1.

FIG. 6 is an alternate embodiment of the guide member shown in FIG. 5.

Referring to FIG. 1 the present structure 10 is illustrated in the normal submerged position at an offshore body of water for the purpose of drilling exploratory gas or oil wells. To fully explore the substratum, diverse wells are normally drilled to assume one or more directions radially outwardly from platform 10 in the manner shown in FIG. 2. The marine platform comprises in essence a deck 11 which is supported above the waters surface by downwardly extending legs 12 and 13. The instant platform lacks uniqueness in itself, being in general of a well known design for a stable vehicle whereby to drill such offshore wells.

While only two support legs such as 12 and 13 are shown it is appreciated that this is merely an illustrative embodiment into which the invention is incorporated. The respective legs may constitute any reasonable number depending on the condition of the substrate, the depth of the water and other design and engineering factors.

The substantially elongated legs 12 and 13 are normally cylindrical in shape. In the instance of some platforms, legs 12 and 13 will contain controllable buoyancy systems for transferring water to and from the legs whereby the platform can be floated into location and subsequently controllably submerged into place by adjusting the buoyancy.

Each leg includes means therein for guiding one or more anchoring piles 14 which extend from the leg lower end are are imbedded to a predetermined depth into the substratum. Piles 14 as showing are secured to and extend from the respective legs. Such anchoring may be supplemented by other piles judiciously connected to the platform and buried in the substrate.

To provide platform 10 with stability regardless of water turbulence and weather at the offshore location,a series of vertically spaced cross-braces l6 and 17 extend between, and are rigidly connected to the respective legs. The number and size of such braces is dependent upon the depth of the water in which the platform is used as well as on other design considerations.

At the platform top side, deck 11 supports a drilling rig which embodies in essence a derrick 18 adapted to raise or lower and suspend a drill string, draw works 19, and rotary table 21. One or more cranes such as 20 are spaced about the deck to handle materials and transfer equipment to and from boats. Rotary table 21 provides a means for the drill string to be controllably rotated for insertion into the well. In the normal manner, derrick 18 is disposed in a generally vertical disposition. Further, said derrick as well as the draw works is so mounted as to be horizontally movable about the decks surface whereby to be oriented over a particular deck openmg.

The mobility of rig units 18 and 19 along deck 1 1 is necessitated to permit alignment over any of the widespread conductors for drilling in diverse directions.

The respective drill conductors 22, 23, 24 and 26 are shown in FIG. 2 radiating from the four sides of platform 10. It is appreciated however that said conductors may be aligned in any direction as required. Particularly, in the instance when a productive field lies to one side of platform 10, it may be advisable to direct a number of wells toward the productive area rather than in alternate directions. In any event, platform 10 is initially provided with conductor guide means adapted to receive a downwardly moving, normally straight conductor such as 22, and to guide the latter into a desired curved configuration.

The upper end of curved drilling conductor 22 is disposed in substantially vertical alignment, and terminates adjacent to the rotary table 21. In such position, a derrick supported drill string including drill pipe and bit, can be lowered into the con ductor. Upon rotation, the string thus is caused to assume the direction determined by said conductor.

Drill guide conductor 22 is normally formed of an elongated cylindrical member approximately 16 to 36 inches in diameter, fabricated of steel pipe or tubing, normally made up in short incremental lengths. Again, following normal practice, conductor pipe 22 is lowered into place from deck I 1 until the lower end is disposed adjacent the ocean floor. The conductor pipe is progressively elongated by welding incremental shorter sections to the upper end as said conductor is lowered.

therein adapted to receive the outer surface of a conductor I pipe. To facilitate movement of a conductor through the longitudinal passage, said guide unit or collar 27 can be provided with a series of peripherally arranged, journalled roller assemblies32 or 43, as shown in FIGS. 5 or 6. The rollers are so spaced about the conductor to maintain the latter in a vertical disposition as the conductor descends, and to minimize wall friction which would deter passage of the conductor. Collar 27 is registered through an opening in deck 11 whereby drilling derrick 18 can be aligned over said opening such that the drill string can be lowered vertically into the conductor upper end.

Lower guide units 28, 29 and 31 respectively are disposed sequentially beneath collar unit 27. Said lower units are successively ofi'set horizontally, one from the other, a predetermined distance to achieve the necessary curvature in the overall conductor length and to define an arcuate center line as the latter is inserted. Units 28, 29 and 31 are mounted as shown in FIG. 3, to cross-bracing 16 whereby to rigidly position the unit in spite of both horizontally and vertically oriented displacing forces exerted thereagainst.

Referring to FIG. 3, each of said guide units 28, 29 and 31 includes in essence a downwardly tapered shoe 34 cooperatively arranged with a ring or sleeve 36 and fastened into place with gussets 30. Shoe 34 serves the essential function of slidably receiving the lower end of a drill conductor 23 on the shoes'upper surface as the conductor is passed downwardly from the guide unit thereabove. The conductor lower end is preferably slidably received on a smooth tapered surface to be urged therealong as the conductor advances, into the center opening of ring 36. In one embodiment, shoe 34 comprises a frusto-conical member having the wide upper end thereof sufficient diameter to receive the conductor end. Further, said conical member is displaced laterally, and axially aligned with the adjacent guide unit, to register the downwardly moving conductor and to urge the latter laterally from its path into said ring member 36 and rollers 32 and 43.

, Referring to FIG. 4, an alternate embodiment of the conductor guide is illustrated. Said embodiment includes a shoe portion 37 comprising a partial conical segment having an inwardly sloping surface directed toward a ring deflector 38.

g The sloping guide surface of shoe 37 is bordered by a pair of upstanding edges 39 and 41 that extend from the shoe upper end to said ring deflector. The inner surface of said shoe is free of obstructions whereby to best function as a guide surface for a downwardly moving conductor to urge the latter into said deflector 38.

Ring member 36 comprises in its most basic form, and as shown in FIG. 3, a generally circular body defining an internal through passage 40 sufiiciently large to slidably register the conductor 23. However, to avoid the friction ordinarily experienced by rubbing contact between a lowering drill conductor and ring 36, the latter can comprise, or be provided with one or more roller assemblies mounted in a horizontal plane. Such an arrangement permits rolling movement and ease of passage upon contact with the advancing conductor.

As above mentioned, and as shown in FIG. 5, in one embodiment conductor ring comprises a series of 3 or more peripherally arranged roller assemblies 32, each of which includes an axial shaft which is joumalled to end bearings or the like. The respective terminally mounted roller assemblies are fixed to a suitable frame or base plate 45 which in turn is secured tothe platform bracing members and/or legs.

The roller arrangement for guiding a conductor as the latter is lowered through the respective guide units can comprise a number of arrangements to define passage 37. An alternate embodiment of the latter is shown in FIG. 6 and comprises a pair of spaced apart contoured drums 42 and 43. The latter are journalled to a support frame 44 through end-mounted bearing 46 and 47. The parallel mounted drums define a variable center passage 48 therebetween whereby to reduce the number of rollers to a minimum and to accommodate varying sizes of conductor members which may be directed through .the guide section.

ductor 23 comprises a cylindrical tubular element having a sufl'icient diameter to freely accommodate a rotating drill string passed therethrough. Toward further expediting passage of the conductor 23 lower end along the respective guide shoe surfaces, the conductor lower end can be contoured or formed as shown in FIG. 1, to best engage the corresponding shoe surface. The individual sections of conductor 23, prior to being fabricated, can be preformed to a predetermined curvature or they can be provided from straight chordal sections with the respective ends cut at a proper angle such that when said ends are fastened to the next sequential section, the two will define a desired degree of curvature.

In some instances only a minimal angle of deviation is desired. In such an instance, thin walled conductor pipe can be utilized. Thus, the guide conductor can be formed to the desired degree of curvature during installation. Utilizing this method, straight lengths of pipe are made up and thereafter welded together. After each successive weld the pipe is lowered to permit fastening another length to the upper end. The weight of the pipe is normally suflicient to cause deflection thereto as it passes through the conductor guide. if additional weight is necessitated, an external axial load can be provided through the use of a pile driver applied to the top end either as a weight or by driving.

The process of adding and advancing in any instance is continued until the lower end of the conductor enters the ocean floor. Additionalsections are then made up and the conductor is successively driven and elongated to the desired depth.

The number of conductors inserted through the respective guide units is contingent on the degree of exploratory work to be done at a particular location. Should it become determined that the entire area is lacking in prospective productability characteristics, as a matter of economy, no further conductors will be inserted.

it is appreciated that with presently available well drilling equipment and materials, there are limitations within which the conductors angular deviation must be confined. A reasonable latitude to such a deviation is found by experience to be about 3 per ft. of depth.

Obviously many modifications and variations of the invention, as hereinafter set forth, may be made without departing from the spirit and scope thereof, and therefore, only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. An anchored marine structure at an offshore body of water adapted for directional drilling of under water wells which comprises;

a working deck positioned above the water's surface and holdingwell drilling equipment,

at least one elongated leg supportably connected to said working deck and extending downwardly to the floor of said body of water,

pile means connected to said structure and depending from the lower end thereof being imbedded in the substratum of said body of water to rigidly fix said structure in place,

conductor guide means carried on said structure and being adapted to slidably receive and deflect a drill guide conductor passed downwardly therethrough,

said conductor guide means including, discrete guide units spaced vertically apart in substantial vertical alignment and being deviated horizontally from said substantially vertical alignment to define an arcuate center line along the common axis of said respective guide units.

2. In an apparatus as defined in claim 1 including; an elongated cylindrical conductor registered in said substantially vertically aligned discrete guide units, said cylindrical conductor being deformed thereby into an arcuate configuration.

3. In an apparatus as defined in claim 1 including; a collar depending from said working deck and having a vertically aligned guide passage extending therethrough, said guide passage being adapted to slidably engage a portion of said conductor whereby to maintain said engaged portion in a generally vertical disposition.

4. In an apparatus as defined in claim 1 wherein said discrete conductor guide unit includes; a ring-like member having a shoe extending upwardly therefrom to slidably receive and urge said conductor lower end in a horizontal direction as the latter descends against said guide unit.

5. In an apparatus as defined in claim 1 wherein said discrete guide unit includes; a shoe having upper and lower ends, a ring carried at the shoe lower end and defining a sufficiently large opening to slidably receive a downwardly moving conductor therethrough and to urge said conductor in a lateral direction.

6. In an apparatus as defined in claim 1 wherein said discrete conductor guide unit includes; a conical member having an upwardly facing inlet which tapers to a lower contracted portion, and a ring carried at said contracted portion defining a sufiiciently large opening to slidably receive said conductor.

7. In an apparatus as defined in claim 4 wherein said shoe includes; a conical segment having an open portion thereof facing in an upward direction to receive the lower end of a conductor.

8. In an apparatus as defined in claim 7 wherein said shoe includes; a segment of a conical section having upstanding edges disposed to contact and guide a conductor.

9. In an apparatus as defined in claim 1, wherein said conductor guide means includes; at least one roller having the iongitudinal axis thereof disposed in a vertical plane and adapted to engage said conductor as the latter is lowered.

10. In an apparatus as defined in claim 1 wherein said con ductor guide means includes; a plurality of joumalled rollers peripherally arranged about an opening therethrough to register and engage said conductor as the latter is lowered from said working deck.

* il I! I. i

Notice of Adverse Decision in Interference In Interference No. 98,366, involving Patent No. 3,670,507, G. E. Mott, and J. J. Ziober, MARINE DRILLING STRUCTURE WITH CURVED DRILL CONDUCTOR, final judgment adverse to the patentees was rendered Aug. 22, 1974, as to claims 1 and 2.

[Ofiez'al Gazette December 24, 1974.] 

1. An anchored marine structure at an offshore body of water adapted for directional drilling of under water wells which comprises; a working deck positioned above the water''s surface and holding well drilling equipment, at least one elongated leg supportably connected to said working deck and extending downwardly to the floor of said body of water, pile means connected to said structure and depending from the lower end thereof being imbedded in the substratum of said body of water to rigidly fix said structure in place, conductor guide means carried on said structure and being adapted to slidably receive and deflect a drill guide conductor passed downwardly therethrough, said conductor guide means including, discrete guide units spaced vertically apart in substantial vertical alignment and being deviated horizontally from said substantially vertical alignment to define an arcuate center line along the common axis of said respective guide units.
 2. In an apparatus as defined in claim 1 including; an elongated cylindrical conductor registered in said substantially vertically aligned discrete guide units, said cylindrical conductor being deformed thereby into an arcuate configuration.
 3. In an apparatus as defined in claim 1 including; a collar depending from said working deck and having a vertically aligned guide passage extending therethrough, said guide passage being adapted to slidably engage a portion of said conductor whereby to maintain said engaged portion in a generally vertical disposition.
 4. In an apparatus as defined in claim 1 wherein said discrete conductor guide unit includes; a ring-like member having a shoe extending upwardly therefrom to slidably receive and urge said conductor lower end in a horizontal direction as the latter descends against said guide unit.
 5. In an apparatus as defined in claim 1 wherein said discrete guide unit includes; a shoe having upper and lower ends, a ring carried at the shoe lower end and defining a sufficiently large opening to slidably receive a downwardly moving conductor therethrough and to urge said conductor in a lateral direction.
 6. In an apparatus as defined in claim 1 wherein said discrete conductor guide unit includes; a conical member having an upwardly facing inlet which tapers to a lower contracted portion, and a ring carried at said contracted portion defining a sufficiently large opening to slidably receive said conductor.
 7. In an apparatus as defined in claim 4 wherein said shoe includes; a conical segment having an open portion thereof facing in an upward direction to receive the lower end of a conductor.
 8. In an apparatus as defined in claim 7 wherein said shoe includes; a segment of a coniCal section having upstanding edges disposed to contact and guide a conductor.
 9. In an apparatus as defined in claim 1, wherein said conductor guide means includes; at least one roller having the longitudinal axis thereof disposed in a vertical plane and adapted to engage said conductor as the latter is lowered.
 10. In an apparatus as defined in claim 1 wherein said conductor guide means includes; a plurality of journalled rollers peripherally arranged about an opening therethrough to register and engage said conductor as the latter is lowered from said working deck. 